The dispensing of liquid chemical products from one or more chemical receptacles is a common requirement of many industries, such as the laundry, textile, ware wash, healthcare instruments, and food processing industries. For example, in an industrial laundry facility, one of several operating washing machines will require, from time to time, aqueous solutions containing quantities of alkaloid, detergent, bleach, starch, softener and/or sour. Increasingly, such industries have turned to automated methods and systems for dispensing chemical products. Such automated methods and systems provide increased control of product use and reduce human contact with potentially hazardous chemicals.
Contemporary automatic chemical dispensing systems used in the commercial washing industry typically rely on pumps to deliver liquid chemical products from bulk storage containers. Generally, these pumps deliver raw product to a washing machine via a flush manifold, where the product is mixed with a diluent, such as water, that delivers the chemical product to the machine. A typical chemical dispensing system used to supply a washing machine will include a controller that is coupled to one or more peristaltic pumps in a pump-stand by a plurality of dedicated signal lines. The controller will also typically be coupled to a washing machine interface by another plurality of dedicated signal lines, so that the controller is provided with signals indicating the operational state of the machine. In operation, the machine interface transforms high voltage trigger signals generated by the washing machine into lower voltage signals suitable for the controller, and transmits these low voltage trigger signals to the controller over the set of dedicated signal lines, which are typically in the form of a multi-conductor cable. In response to these individual trigger signals, the controller will individually activate one or more of the pump-stands over another set of dedicated lines so that the pumps dispense a desired amount of a chemical product into the flush line. The chemicals are then are mixed with a dilutant before being delivered to the machine.
In the chemical dispensing system described above, the controller is connected to each washing machine trigger signal output and pump by a dedicated line, and the controller directly activates and deactivates each of the pumps. This arrangement, while generally satisfactory for its intended purpose, places practical limits on how many trigger signals and pumps can be connected to a single controller and creates a need for large numbers of wires and controller input ports. Installation of these types of systems can be cumbersome since installers must keep track of each signal line and ensure that the each line couples the proper controller port to the proper trigger signal source or pump. An incorrect connection may result in the wrong chemical being dispensed at the wrong time by the system, and may not be immediately apparent, resulting in many incorrectly processed loads and resulting monetary losses. Moreover, because the controller is merely switching the pumps on and off for an amount of time expected to provide a desired amount of chemical to the flush manifold, the controller receives no feedback regarding whether the pump is actually dispensing the amount of product desired.
Chemical dispensing systems employed with commercial washing machines typically employ peristaltic pumps to minimize both operator and system component contact with the chemical products, which are often corrosive and toxic. Peristaltic pumps of this type include a flexible tube (or squeeze tube) and a rotor with one or more rollers located in a pump chamber. The one or more rollers compress a section of the squeeze tube against a wall of a pump chamber, pinching off the section of squeeze tube. When the rotor is rotated, the location of the pinched section of the squeeze tube moves along the length of the tube, thereby forcing, or pumping, fluid through the tube. The amount of fluid pumped per unit time tends to vary from pump to pump, depending on multiple variables such as the speed with which the rotor turns, the interior diameter of the squeeze tube, and the viscosity of the product being dispensed. Therefore, system installers must perform calibration measurements on each pump so that the system controller dispenses accurate amounts of product. This requirement for calibrating each pump during installation greatly increases installation time and expense.
Squeeze tubes are also subject to wear over time from the repeated compression and pulling of the rollers, which causes the volume of chemical pumped by the pump-stand to vary over time. Worn out squeeze tubes must also be periodically replaced to prevent tube failure. Squeeze tube replacement can be a cumbersome endeavor, as chemical product often leaks from the feed lines when the seal is broken between the squeeze tube and feeder tubes. In addition to causing a loss of product and undesirably exposing workers to potentially hazardous chemicals, the spilled product may also contaminate the surfaces of the squeeze tube and pump chamber. If the chemical product is not sufficiently cleaned from these surfaces, the resulting sticky residue can cause the roller to pull the squeeze tube through the pump chamber so that the tube becomes damaged or tangled, resulting in pump failure and further potential product spills. In addition, because the controller cannot determine that the pump is not dispensing the correct amount of product, any processed wash loads that rely on the failed pump will have to be re-processed. Further, because the timing of the pump failure may be difficult to determine, multiple wash loads may have to be reprocessed.
Therefore, there is a need in the art for improved chemical dispensing system components and methods that more accurately and reliably control the dispensing of chemical products into washing machines, and that reduce the maintenance burden and number of potential failure modes associated with peristaltic pumps.